HAs anyone used EVAL-ADIS-FX3 + ADIS16475-x/PCB with an extenal clock

Dear All,

I need to acquire data from IMU ADIS16475 and test a EKF quaternion from IMU against an optical system. 

I would use the EVAL-ADIS-FX3 + ADIS16475-x/PCB in order to acquire the data form IMU but I need to synchronize the acquisition with the optical camera. 

Is it possible to use a external trigger as input ( from the camera) to command the IMU acquisition? or reverse is it possible to bring outside the clock from the EVAL-ADIS-FX3 ?

Many many thanks

MAssimo

  • Hello MAssimo,

    There's two ways you can tackle this problem:

    1) Synchronize the IMU sampling with the camera trigger, then synchronize the data acquisition with the IMU data ready

    2) Configure the FX3 to acquire data on the camera trigger (read asynchronous from the IMU)

    Option 1 may give better performance/behavior, but will be a little more tricky to set up:

    By default, the digital I/O pins on the EVAL-ADIS-FX3 will float. You should be able to connect an external clock signal to the DIO2 probe point, which maps to the SYNC input on the ADIS1647x IMU. See image below:

    To synchronize the IMU sampling with the external sync signal, you have to configure the IMU MSC_CTRL register based on the desired sampling mode. Note, to use direct external sync mode, the external sync clock must run at ~2KHz. If the camera triggers runs at a lower rate, I would recommend using the scaled sync sample mode to upscale the camera trigger rate to 2KHz.

    For option 2, you can connect the camera signal to any DIO (except DIO1, which is the data ready output), and configure the EVAL-ADIS-FX3 to use that pin as the "data ready" signal in the config form. Then, any SPI transactions with data ready active enabled will start when the camera trigger is received. You can then use the register logging form (or matlab/python/labview interface code) to read inertial data synchronous to the camera trigger. To improve noise performance, you might also want to configure the IMU ODR to match the camera trigger rate (using the DEC_RATE register).

    -Alex Nolan

  • Thank you  !

      - What is the frame update rate, for your camera system?